Mud check valves in drilling apparatus (wells)

ABSTRACT

A check valve for connection with the top end of a drillstring as a mud saver comprises a tubular valve member (18) which is axially shiftable within a tubular body (10) through a sleeve seal (19) which is mounted in the body (10) and which cooperates with ports in the wall of the tubular valve member (18) and which is disposed adjacent a downstream end of the tubular valve member. A compression spring (20) urges the tubular valve member (18) in the upstream direction into abutment with an upstream stop (15). The downstream end of the tubular valve member is closed by means of a frangible glass disc (21). The sleeve seal (19) is also axially shiftable in the body (10) in an upstream direction away from a downstream stop (17) and the compression spring (20) urges the sleeve seal (19) in the downstream direction. In a compact arrangement, the tubular valve member (18) is housed within an upstream hollow pin (30) of a saver sub particularly suited to a top drive arrangement.

BACKGROUND OF THE INVENTION

This invention relates to a check valve for connection with the top endof a drillstring as a mud-saver.

Mud-saver valves are installed at the lower end of a kelly for thepurpose of checking outflow of drilling fluid from the kelly ondisconnection of the kelly joint. Such mud-saver valves are alsoinstalled in a top drive system for the same purpose.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a check valve forconnection with the top end of a drillstring as a mud saver, comprisinga tubular valve member axially shiftable within a tubular body through asleeve seal mounted in the body and which cooperates with ports in thewall of the tubular valve member which ports are disposed adjacent adownstream end of the tubular valve member, spring means urging thetubular valve member in the upstream direction and into abutment with afirst stop means, and a closure closing the downstream end of thetubular valve member; characterized in that the sleeve seal is axiallyshiftable in the body in an upstream direction away from a second stopmeans, and in that the said spring means urges the sleeve seal in thedownstream direction.

Further, according to the present invention, there is provided a checkvalve for connection with the top end of a drillstring as a mud saver,comprising a tubular valve member axially shiftable within a tubularbody through a sleeve seal mounted in the body and which cooperates withports in the wall of the tubular valve member which ports are disposedadjacent a downstream end of the tubular valve member, spring meansurging the tubular valve member in the upstream direction and intoabutment with a first stop means, and a closure closing the downstreamend of the tubular valve member; characterized in that the body is asaver sub having an upper externally screw-threaded hollow pin forconnection with a drive member, and in that the said tubular valvemember is housed within said hollow pin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional elevation of a first embodiment of a check valvein accordance with the present invention; and

FIG. 2 is a sectional elevation similar to FIG. 1, but showing a secondembodiment of a check valve in accordance with the present invention andconnected with parts of a top drive and a drillstring.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 of the drawings, the check valve consists of a body 10 whichis adapted for connecting in line coaxially with a kelly (not shown) anda drillstring (not shown). Thus, the check valve is inserted at thekelly joint which is the usual point of connection between the kelly andthe drillstring. The top or input end of the check valve has a standardtapered screw-threaded box or socket 11; and the other end of the checkvalve has a standard tapered screw-threaded hollow pin 12. Alternativeconfigurations of screw-threaded connectors may be chosen according tospecific requirements, for example for use in a top drive system or inany arrangement of tubulars to check fluid loss.

An intermediate portion of the valve body 10 defines a cylindrical bore13 at the upper end of which there is provided a screw-threaded portion14 and a first or upstream stop means in the form of an annularretaining collar 15 which incorporates a fluid-tight seal 16. The lowerend of the bore 13 defines a seconds or downstream stop means in theform of a step 17 which, in conjunction with the retaining collar 15locates a fluid flow control means consisting of a tubular valve member18, a sleeve seal 19, a compression spring 20, and a frangible closurein the form of a toughened soda-lime glass disc 21.

More particularly, the upper end of the tubular valve member 18 isflanged to define an annular piston 22 which slidably engages the bore13 and provides an upper land for the compression spring 20. The lowerend or downstream portion of the tubular valve member 18 is providedwith streamlined openings or ports 23, and the same vicinity of thetubular valve member 18 is engaged by the sleeve seal 19 which is alsoslidably received in the bore 13 and is provided with sliding seals 24.The upper end face of the sleeve seal 19 provides a land for the lowerend of the compression spring 20. The annular space between the tubularvalve member 18 and the bore 13 is in communication with the interior ofthe tubular valve member 18 by way of four equi-angularly spaced slots25 which serve to "vent" the said annular space and also allow forclearance therefrom of particles or other solid matter which may havesettled out from the drilling fluid.

The glass disc 21 is located in a recess at the downstream end of thetubular valve member 18 together with a fluid tight seal 26; and thedisc 21 is retained by a snap ring 27.

The strength or force of the compression spring 20 is determined withreference to the weight of a column of drilling mud above the checkvalve in the kelly or other tubular whilst the fluid is static. Thus,the spring strength is sufficient to support the weight of the mudcolumn with the upper end of the tubular valve member 18 in abutmentwith the retaining collar 15 and the ports 23 within the sleeve seal 19.In this condition, the mud column within the kelly or other tubular isretained and the lower joint with the drillstring may be disconnectedwithout any significant loss of drilling fluid.

In resuming drilling operations and mud pumping, the tubular valvemember 18 is shifted axially downwards against the compression spring 20by virtue of pressure drop over the tubular valve member 18 during flowof drilling fluid. Thus, the ports 23 discharge into the valve body 10immediately below the sleeve seal 19, the main flow of drilling fluidbeing through the tubular valve member 18 and the ports 23.

Whilst the check valve is closed, and with the drillstring stillconnected, any "pressure kicks" within the drillstring will act on thelower end face of the sleeve seal 19 which may shift axially upwardsagainst the compression spring 20 thereby relieving the pressure kickthrough the ports 23. It will be understood that the arrangementdescribed is capable of permitting virtually full reverse flow in theevent of a severe pressure kick.

In the event that it becomes necessary to deploy wireline toolsdownhole, straight-through access to the drillstring is gained by firstdropping a cone-tipped sinker on a wireline into the kelly or top driveso that the sinker tip penetrates the stressed surface of the glass disc21 causing the latter to disintegrate. Wireline tools may then bedeployed; and a new or fresh glass disc may be fitted subsequently. Thechoice of a toughened soda-lime glass is preferred because this materialreliably disintegrates to a fine particulate condition, thus reducingthe risk of larger glass fragments impeding or interfering with thewireline tools.

In FIG. 2 of the drawings, parts corresponding with those in FIG. 1 aregiven the reference numerals used in FIG. 1.

In FIG. 2, the body 10A of the check valve is configured as a saver subwhich is used in the industry as the preferred connection between a topdrive shaft 28 and drillstring 29. The downstream pin of a saver sub canbe recut to compensate for wear resulting from repeatedconnection/disconnection to and from the drillstring. When furtherrecutting of the saver sub is impossible, then the entire saver sub isrelatively cheap to replace.

Particularly in a top drive arrangement, there is a practical limit tothe axial dimension of saver sub which can be accommodated withoutcompromising the vertical action, of the top drive arrangement.Accordingly, the check valve described with reference to FIG. 1 abovemay not be suitable with some top drive arrangements.

In order to accomplish an axially compact check valve, the tubular valvemember 18 and the sleeve seal 19A of FIG. 2 are accommodatedsubstantially within the upstream hollow pin 30 of the saver sub.Moreover, the pin 30 is provided with an upstream non-threaded extension31 which is accommodated within the top drive shaft 28 and providesadditional axial length whereby the appropriate check valve action canbe accomplished having regard to required spring rate of the spring 20and the necessary travel of the tubular valve member 18.

A conventional standard saver sub has a straight-through bore. However,the present saver sub has an enlarged middle portion defining a chamber32 which accommodates the downstream end portion of the tubular valvemember 18 and discharge from the ports 23 when the check valve isactioned by operation of the mud pumps.

In the FIG. 2 embodiment, the toughened soda-lime glass disc 21A carriesa relatively small check valve 33 of the ball-check type and which isfitted to the glass disc 21A through a central opening therein. Thecheck valve 33 allows a driller to detect pressures within thedrillstring with the main check valve closed and with the circulationstopped. It will be understood that the small check valve 33 isdisposable in the event that the facility for wire-line access is used.

In the FIG. 2 embodiment, the upstream stop means consists of a circlip15A. Also, the annular space occupied by the compression spring 20 isvented to the inside of the tubular valve member 18 through openings25A. Also, the sleeve seal 19A, as can be seen by inspection of thedrawing of FIG. 2, consists of a moulded sleeve casing with insertedring-seals.

I claim:
 1. A check valve for connection with the top end of adrillstring as a mud saver, comprising a tubular valve member (18)axially shiftable within a tubular body (10, 10A) through a sleeve seal(19, 19A) mounted in the body (10, 10A) and which cooperates with ports(23) in the wall of the tubular valve member (18) which ports (23) aredisposed adjacent a downstream end of the tubular valve member (18),spring means (20) urging the tubular valve member (18) in the upstreamdirection and into abutment with a first stop means, and a closure (21,2A) closing the downstream end of the tubular valve member (18);characterized in that the sleeve seal (19,19A) is axially shiftable inthe body (10, 10A) in an upstream direction away from a second stopmeans (17), and in that the said spring means (20) urges the sleeve seal(19A) in the downstream direction.
 2. A check valve according to claim1, characterized in that the closure (21, 21A) is of a frangiblematerial.
 3. A check valve according to claim 1, characterized in thatthe closure (21, 21A) is a disc of toughened glass.
 4. A check valveaccording to claim 3 characterized in that the closure (21, 21A) is adisc of toughened soda-lime glass.
 5. A check valve according to claim 1characterized in that the closure (21A) has a second check valve (33)mounted therein.
 6. A check valve according to claim 1 characterized inthat the body (10A) is a saver sub having an upper externallyscrew-threaded hollow pin (30) for connection with a drive member (28),and in that the said tubular valve member (18) is housed within saidhollow pin (30).
 7. A check valve according to claim 6, characterized inthat said hollow pin (30) has an upstream non-threaded extension (31).8. A check valve for connection with the top end of a drillstring as amud saver, comprising a tubular valve member (18) axially shiftablewithin a tubular body (10A) through a sleeve seal (19A) mounted in thebody (10A) and which cooperates with ports (23) in the wall of thetubular valve member (18) which ports (23) are disposed adjacent adownstream end of the tubular valve member (18), spring means (20)urging the tubular valve member (18) in the upstream direction and intoabutment with a first stop means, and a closure (21A) closing thedownstream end of the tubular valve member (18); characterized in thatthe body (10A) is a saver sub having an upper externally screw-threadedhollow pin (30) for connection with a drive member (28), and in that thesaid tubular valve member (18) is housed within said hollow pin (30). 9.A check valve according to claim 8; characterized in that said hollowpin (30) has an upstream non-threaded extension (31).